Document XOBQgD9m11RLNEQRB00zYvp7K

--/ Monsanto Chbmicaw- Plastics AN INDIRECT AROCLOR HEATER for UNIT CHEMICAL OPERATIONS Momonto Tachnieol Bulletin No. P*I30 September, 1949 Monsanto Chemical Company St. Loui* (4), Missouri Aroclor* 1248 (chlorinated biphenyl) is an ideal nonflammable liquid phase heai*transfer medium for temperatures up to 300C. This bulletin describes the physical properties of Aroclor 1248 and illustrates the design and operation of heaters that have been used successfully by Monsanto plants during the past seven years. The units described are gas fired and the capacities are in the range of 200,000 to 400,000 D.t.u. per hour. Other larger commercial installations using Aroclor 1248 have capacilies ranging up to 2,000,000 B.t.u. per hour. Also small electrically heated stationary and portable units with capac ities around 40,000 B.t.u. per hour,using Aroclor 1248 as the heattransfer medium,art in service. Several leading manufacturers of heating equipment are in position to build or offer Aroclor heating units to meet specific requirements. **. U. Pat. Otflr* 0m 1n m -n M >o rn or 2 5 >5 x O -* z m o X f ! 3 H irt oo CD c 3 f y If Sr The Intemiallnn contained In dila bulletin I*. I* e beet knowl.dft, uu and accurate, but all rcrommctvtationc at r made without (uarantrt. alne* th condition* a( urr arc baywnd control. The Mon.anto Chemical C<imcny dta'lalm. any liability incurred In connection wilt. the uce ot there data or out (cotton*. t'lo'lirrmorf, nntMn comalncd Kccoln chotl be conalrueO aa a recononendotlon to aatallna i.eienti re.mn, any malarial ot lla uae. any oe4r< in wHh 0N5 078230 He,Minted from inuUHTKIAL AND ENGINEERING CHEMISTRY, Voi. 41, Page 1341, July 1949 (Copyright 1049 by the American Chemical 8odely and reprinted by permission of the eopyriglit owner An Indirect Aroclor Heater for Unit Chemical Operations Mr.AUK McAKDLK', L. C. GAHKETT, AND V. G. BKNIGNUS' Nonnonlo Chemical Company^ Annirlon, Ala. The tbaracterlslles of Aroclor 1249 Indirtle tlret It la an Ideal llquit' phaae liMl-riclige medium for Uiniprraluiti up to 900* C. This article dhctitMi ita 8prat Flammability, When a tube ruptures in a liquid heattransfer system under high pressure, a spray or mist forms. The possible Are hasard under thoso conditions requires considera proprrtiea anti lllualralea the design and operation of tions not oovored by the foregoing discussions relative to the mo- healer* that have been uaed successfully by Momnnto tcriai in the liquid form, fo thoir comprehensive study of plants during (lie paet seven year*. AammabUity of the higher boiling liquids and their trusts, Sulli van, Wolfe, and Zisman (8) determined the spray flammability IN CERTAIN manufacturing processes of the Monsanto Cliemleal Comimny, it wu nooeasary to employ a noneom- limit of numerous materials in accordance with the percentage of oxygon required for combustion. This value was then correlated buatlUa heat-transfer medium at pleasures of 80 pounds per with the results of incendiary firing tests of the fluids conducted square Inch or lorn and temperature# up to 800* C. The following at tlio Naval Proving Ground, DaMgren, Va. The oxygen re general properties of a hcal-exchangu medium wore required: quirement for Aroclor 1248 oombustion In the spray flammability Freedom from fire haaards. Ytonaitics to permit pumping at room temperatures. Rotting point sufficiently above 800* C. to assure a liquid con limit studies was found to be 04%. Fluids requiring over 45 to 50% oxygen in the spray test failed to cause a Are in the incendi ary tost. These results establish the nonflammable and nonootu- dition at all timet. Stability againat heat, will) enough aafety factor to accommo date aocidtHiUJ overheating. Controllable valorisation losses. a __ Freedom from corrosive action against valvca, piping, tank jackets, etc., made of call Iron and tooIs, bronse, and atainlcsa atecl. Freedom from toxicity haxard. bustible qualities of Aroclor 1248. VISCOSITY CONSIDERATIONS Cold Flow. For most inside installations oentrifugel pumps will handle Aroclor at reduced rate* without preheating. Experi ence confirms this. Outside installations have been started at Aroclor, chlorinated biphenyl (registered in V. 8. Patent 0* C. by heating the pump and food lino until circulation through Offler), was selected. The pertinent physical characteristics relative to ita uso aa a heat-transfer medium arc given in Table I. Tadlb ]. Physical Pbopbrtibs or Ahoclqr 1248 IKKKIMJM FROM FINK HAZARDS Flash Point. limitations of this teat for the prediction of the Are baxard of relatively nonvolatile organic fluids have been Apiaranca AUaolutc density, g./ml. Praetioally olorlacs nobUo llqnM *C. CP.) recognised by the American Society for Testing Materials com mittee (8,4). Finn Point is a more aignifieant measurement. The Under writers' laboratories (JO) state that Are tests more truly reflect, the (lack of) lire hasard of Aroelor. BroNTANNOVa Ionition TbmphnaTUBB. The eombualion- Almolute viacolity, ceatipoiaes n J13> (M) <672$ resistlng qualities of Aroelor 1248 are indicated by ita high spon taneous ignition temperature of 704* C. (1299* F.) determined by Sullivan, Wolfe, and Zisman (P), using the oonvenient apparatus diwcribcd by Rorlman, Beatty, and Heron,(8). Under condition# of industrial use the spontaneous ignition temperature will bo determined by factors including the nature of Ute hot surface, tho amount df liquid impinging on it, the volume of eneloaod space, and the ventilation. Thermal conducUvIty, B.t.u./bour/aq. foot/ F./loot DJalillalloa rente. A.8.T .M, P2U, C Flaal' imint. Cleveland open cup. AB.T.M, D 02-46, * C. Fire poiot, Cleveland oprn cur, A.S.T.M. D 92-46 Pour point. A B.T.M. D-7. * C. 0.0614 0 0WS 0 0800 >40 476 IBS- ISO NnM 40 (B6 60 (ISO 100 (212) An accidental failure in a heating syetein demonstrated the nonflammaMUty of Aroclor 1248 ana ite freedom from the hasard of Arc propagation. An operator's failure to start the circulation of the treat-transfer medium when Die gas heater was on resulted In oxooasivc coil temperatures and caused the lower coil to soften and sag into the Are chamber. A weld ruptured and Aroelor 1248poured into tho red-hot fire chamber in contact with the flame. Dense smoke arose from the hcator but there wasno external fire. After the gas flame was eul off, the smoking topjNKl. 1 Pmrnt arldreaa, Monaanto Chamleal Company. Organic Chemical* JMvMan, Bl. Leu)*, Mo. 1 J'rrwnl addrcaa, Monunto Chernies! Company, Ptioapbato Divtsioa, It. laula. Me. Specific volume, ml./g. Spec!fie beat, eaf./g./* C. Vapor preoaurc. mm Hg 0 SS6 0 70* 0 724 0.7S7 0.100 I2S7 im 266 IWJ) |l0> 672) HCNS 078231 1342 INDUSTRIAL AND ENGINEERING CHEMISTRY Vol. 41, N T Tails II. Stability or Aboclob 1249 Hbatbd roi 30 House 9.079 0 1U 0 199 0-299 0 249 Table HI. 8tabiuty or Aboclob 1248 Continuously Heated at 280* and 330* C. 0 079 0-119 0.199 0 194 0.291 0.249 0 #10 0 923 1.141 1.992 Tablb IV. Oab Akaltiis or Aboolob 1248 Hbatro 4 House at 900* C. and 310 Povndb BBB SouABi Inch Pbbsbvbe Oh % Carbon dlgildl Sirlw* woaoiid* from ,fr* m--Sir <% by *Hbt HCi) Pvter t* ipoor After wtewn Uib bester had bsen effected to tbkt the iytem oould operate Dormally. BOIIJNG POINT Operating experience has shown that the boiling point of Aroelor 1248 (940* C. at 780 mm.) is enough above tbs 300* C. operating limit to prevent trouble from this cause. At the maxi mum operating temperature the vapor prearure is less than 0.5 atmosphere. HEAT STABILITY In order to establish a maximum practical operating tempera ture, the stability of the material when heated to elevated tem peratures In the presenoa of Iron was noted. A slow stream of nitrogen was paassd over the hot Arooior to sweep the deoora- pontUon products Into a caustic trap. The amount of acidic material was determined and calculated as hydrochloric acid. The results given in Table II indicate the aUMlity of Arocior 1248 whan individual samples were heeled for 90 hours at the given "nnperatures. The decom position is very low at temperatures up to 800* C. The stability of Arocior 1248 in contact with L iron continuously heated at 280* and 330* C. is indicated by Table III. These test results indi cate that Arocior 1248 in con tact with iron oan bs used satiefsetorily at temperatures up to 800* C. The National Board of Firs Underwriters (to) reported that "decomposition of the product lArooior 1248) wss not appreci able at temperatures balow 400* C., but became laorea* Ingly apparent at higher tem perature*." at 340* C. fitted with an internal |u burner eo that tbs Xia flame impinged directly on thn mirfae* of the Aroeier nahreto of the gases produced under these condition* inciwfcd 0.8% carbon monoxide. 0-17% oxygen (derived from the air), 0.96% hydrogen chioriao, 2.1% combustible gae calculated as methane, 0,002% chlorine, and no plioegunc. The same worker* etudied the stability of Aroclnr when bealad for 4 hours in an iron pipo at 280* C. under an internal)--min of 210 pounds per square inch', mulling from the intnxiustion tf oompreuod air. Following this treatment and cooling, the um removed from tho ayatem were analyxrd. The aridity oftbe Arocior was determined prior to and after exposure to these con dition*. 7 ha result* given in Table IV reflect an extremely amall umwsI of decomposition under conditions similar to those selected for the practical use of Arocior 1248 a* a heat-transfer medium. In aotual practice using the type of heating unit described helms there baa been no evidence of hydrochloric acid effect **'* os ear* bon deposits have boen noted in the healer, pipes, or valve*. Tho heater* have been operated successfully with combustion gases afc approximately 800* C. in contact with the coil*. At ono time, a spiral coil type of heater was built ami through faulty design a burner tunnel was located 1.5 inches front tbTinch steel pips coil. The radiation from the while-hoi refractory tunnel and the direct impinatmenl of the flame on the pipe hbiiwii the pipe to glow a dark red for a apace of about 2 inches. Tbit unit was operated almost 3 months before a circulation BOMgs occurred. When the line waa opened lump* of carbon were louad to have come loose and moved forward to lodge in the gtrbe valves. The lumps measured about 1 X 2.5 cm. and one face wb* formed to fit the pipe curvature. No hydrochloric acid effect was noted and the system was put back into operation after tbs burnor location was changed. CONTROLLABLE VAPOBIZATION LOSSES The heating systems In which Arocior 1348 is used are sealed except for the expansion tank, which has a loose cover or s vent pipe. Because this tank i* separated from tho stream by a sub stantial length of pipe, the temperature in the lank remains low. Id the light of the relatively low vapor pressure value* for Arocior 1248 (7), and as it is unlikely that the expansion tank wilt ever reach even the 1-mm state (130* C.), there should not W a measurable loss of Arooior from the system. Aotual experience bears out this contention. Othsb Losses. Although Arocior darkens on use, its eharae* tcristies remain the same and replacement has not Iwen found necessary after 7 years of continuous use. Accidental leaks or pills constitute the only observed tosses. PLAN ANO BART SECTION | Their workers analysed the decomposition products of Arooior 1248 heated In the pres ence of hot Iron at 469* C. and also heated in an iron cylinder Figure 1. Heeler MOhS 078232 tkf 1M INDUSTRIAL AND ENGINKKRING CHEMISTRY 1343 ItBMftTAHCB or Bthootural Matcriam to Anocton 1MB Mild ld Phosphor brent* Kd trtM DESIGN AND CONSTRUCTION Hbatino Stbtem. The heating system required to utilize Aroclor 1248 as the exchange medium includes a beater (Figure I), oooler, pump, and expansion tank (Figure 2), and control and safety circuits (Figure 8). - Oaed rsatslanaa, penetration between 1.0 X 10** and 10 X 10** am. per day ar satwaon 0.00014 and 0.0014 inch per year. p. Douetfel mtatansa, prnetratlon between 10 X 10** era. par day ui 1O0 X iO~*cnt. per dav or between 0.00) 4 end 0.014 Ineb per year. e. PeUevias letter iMleatlng mldiMt, iiniBae material may bU*t than tarihautA H totally limaeraad, a* risXl hloaa W beUavad* to e-oma a ijiislh.n Ti>art el teat atrip eapoerd ta atr. KHEKDO.M FROM CORROSIVE ACTION The resistance ot various metal* (7) at 28* and 125* C. ie given In Table V. Similar sludica made at 826* C. (0) indicate that the penetra tion, In incite* per year, for mild steel ia 0.0028; for yellow brass, 0.00047; for copper, 0.00145. Many years of practical operating experience with Aroclor 1248 as a heat^transfer medium bavc shown that the material it prac tically nonoorroeive to valvee, pij>ig, tank jackets, etc., made of east Iron and steels, bronze, and stainless steel. FREEDOM FROM TOXICITY HAZARD Aroelor 124B ie a very ateblo, unreaclive liquid. If the material la spilM on the skin, there are no noticeable ill effects; Irowsver, it is wsll to waali U*e skin with soap and water after contact. A akin bum resulting from accidental contact with hot Aroclor should be treated in tba normal procedure used for hot oil bumc. r adlMfiag to the burned area need not be removed im f union treatment of the burn demands it; in this case p and water or repealed washings with a vegetable oil (linseed oil) should bo used. The vapors emitted by Aroelor 1248 heated to elevated lemparalurei are injurious to tho liver on prolonged exposure and should not be breatlied. Drinker (5) indicated that 0.6 mg, of Aroelor 1246 per cuitie meter of air is the maximum safe amount pcrnikaiibie in workrooms. In commercial heat-transfer installations, the presumption is that the Aroclor is in a closed system free from leaks. Accord ingly, there should be no opportunity for workers to come in con test with vapors from the hot beat-transfer medium. IlBATsa Design. The general requirements of the beater are compactness, ease of construction snd service, and avoidanes of direct Home impingement on the tubes. Direct flame impingement ia prevented by directing the gas flame through an enclosed ehanncl with hslf-thickncsa fire bnek protecting the tubes above until the high temiwratuic of lbs flame ia rvdurod by heat conducted through these bricks and radiated to the two bottom coils. The sisc of the heater ia redussd to a minimum by using only 4.5 incites of insulating fire brick ia the hottest areas and 2 inches of Kaglc No. 66 insulation oo ths cooler spots. Two sices of units arc uarri: One has a maximum capacity of 200,000 B.t.u. per hour, as shown in Figure l. The larger has s range of 200,000 to 400,000 B.t.u The small aicc consista of 90 feet of 1-Inch standard weight steel pipe made into three coils of six pipes each and connected ia series. The larger sise constat* of 144 feet of 1.5-inch standard weight steel pijvc arranged in the same fashion. Results of testa on tin* small-size hosier covering temperatures from 150* to 800* G. show temper*turn rises to 10* to 20* C. in Uie Aruclor whilo circulating at a rate of 15 to 20 gallons per minute. The outlet gas temperature is consistently within 75* C. of thu outM Aroclor temperature. It is observed that the bottom two coils ab sorb the major part of the heat. The small unit indirntri 50 to 60% efficiencies for capacities up to 200,000 B.t.u. per hour when a natural gas of 1000 B.t.u. per cubic foot is burned. A Surface Combustion Company high pressure inspirator and tunnel burner set is used in Una installation. Over-ail hcst-cxchsiige coefficients ((') for the furnnee are in the ranmt of 7 to 10 B.t.u. per hour par square fool per degree Fahrenheit. Over-all heat-exchange coefficients for Aroclor 1248 to water in a double pi|te heat-exchanger made from I 25-inch pipe with a 2-inch pi|*o jacket are in the 120 to 180 range. These figures arc calculated from test results on tuis installation. MCATCR PIPING Figue* 2. Cooler, Tump, aad Expansion Tank Coolxa. A very useful adjunct to the system is a double pipe cooler oa the outlet of the heater shown in Figure 2. By turning water into the jacket, the Aroclor can be cooled sod the temperature of the system lowered. This ta helpful alien it is necessary to coo) a batch before removing it or when an exothermic reaction starts to get out of control. Pump. The pump for circulating the Aroclor 1248 may be any one of a number of standard centrifugal unite designed fur hot liquid service. M0NS 078233 1344 INDUSTRIAL AND INQ1NXKMNQ CHXMISTRT Vol. 41, No. 7 Pips Cenetruetloa (thut-off v*lv*# Control VilvM Cheek velvet tW*t valvat ' IlM VtIVM r,rkln (!nr and gtees Tabu VI. Pinna Dctail (DIimmIhi it laebae) 1 lltrw|C I V* through V* I throat /. through /, */t through */* 1 through I 2'A through * A through Vi 1 through 2 2 A through 9 '/ through Vi 1 through 2 2 ihrouth 0 Vi 1 Vi through 2 _ ........... .............................r AIM Sorawad Flanged Bona In hop and Sold whn poo* tibia. Muft h eleenad to remove Malt Forged atari HrioM. Crane lOOd aerie* Welded Biting*. Crane 200* Barits 80 (to matoh valvea) Maakin* boll* A.9.A. H-10.2 with heiatonal nut* (or rviee below 800* Above uae aHoy to*). Crane in pin A-9.T.M. AM Crane 202h Inraod etae Crane 420 high tarn* perature thread compound Bolt Iron ring Oat or eomttetod Crane JflOflW, eorewed, gate Crane OtlftW. tanfe. gate Crane 23XR. Bang*. gate Crane 1040 XR, eorewed, globe Crane 9090 XR, flanfe, globe Crane 101 XR. Benge, globe Crane 2074 X, eorewed ('ratio 2090 X. flanged Crana ISP X. flanged Coneolldaled 1070 BW, eerewed ConaeMtlalod 1012 W, flanged Ooetae 340D or PurametalUe D- Tyiw 100 PCPR Merab 0-100 lb./tq. loeh gage dphua with Crane 22211 bar etoak valve, lerguaon Beriae R20 Reflet type The Dayton Dotrd Type C pump Jt on example of Ibe lypo required. It elwuld be mode of oast steel and here a watercooled stuffing box tnd water-cooled bearings. The stuffing box should hove room for Bt tart rix rinp of packing and a lantern ring. DuiameUillc No. D-liOor Oarlock No. 234 may be itaed for packing the pomp. An open Impeller ia desirable, aa It will handlo tho eool, more viscous Ikauid on iMrting the system better than wtU a cloned impeller. enough horsepower for tho moat vkaooua eondltioni ia required. I 'imio Btbtbm and Expansion Tank. Tbe detail of tbe piping e>-iem for Aroelor 1348 uaad up to temparaturea of 800* C. (5<3* F.) and 100 pounds per aquare inch proaoure i* given in Table VI. Tha vnlvon and apartaltiaa givan indicate the type re quired. All piping larger than 0.75 inch ia flanged or welded; ex perience haa shown that hot Aroelor penetrates screwed joint* of the larger oiaao. 8teel and cart oteol are used throughout. The system requires an expansion tank located at tha highest leva) of the Insinuation. The si*e of Itos tank t normally about 35% of tbe capacity of the Aroelor system. Connections with valves, made on either aide of the pump, enable the operator to connect a flexible bom and to pump In or out as required. For operation in locations where the Aroelor temperature may drop to where the attendant viscosities may make pumpini im practical in the system as designed, it may be desirable to steam- Jaokrt the Aroelor circulating lines to facilitate rapid start-up. Suitable safely provisions, such as safety pop-off valves, must be installed in tbe steam jaokel system to prevent pressure ruptures whieh would develop if any condensate remained in a closed sys tem during high temperature operation. In ordor to establish operating conditions and to check tbe operation of tiie heater itself, it is often desirable to measure tho temporalures of the Aroelor in and out of the heater and cooler. Items 8,10, and 11 (Figure 3) provide for this. They may be dial tharmomoten or mercury bulb thermometers of any commercially available type recommended for the service. Tablb VII. Safety and Control Eouirwawr 1. High prteat (data*la el bIm) Mareotd DA-21, opva rireuil aa Ugh prawnra. Aatual Mtliaga depend aa Individual leyeet 2. Law preaaurv alarm Moreald DA-21-3, opea elrauil aa law pvaaaura. (dated* -loopac* of pump) Actual aatUaga tfapand aa individual Ipirowt 2. Tharsioetol (dalaela eaeeeatva Itoattng Fanwal 1S002. Contaaia open an tamporatora hraeo obatrueUee 4. Flaal awiteh (dalaela Mareoid Figure 40. 8 P, iwilah. Opaa at law lteeamk)age (ram eya- 0. Flame failure avatam Combualioa Cantrol Corp. FIrare FF8, Flaraa (cut* off gag If pilot flame goea failure control for manual tfolUoo gaa burner tyitema out) 0. Gaa valve (ante off ia iim prveadina davioa* aet) 7. Red light (alarm) 0, llarn (round* alarm) Alarm relay Slop horn ralay Stop horn button TI-yHpAe .C4 -(1gI>D4 l-NO, l 0. Tharmomatar well 0-300* C. mrreurv bulb tharmomatar (vlaual eheck of healer perform ance) 10. Thermometer well 0 300' ('. mricufj. bulb lliermomvt*r (vituel ahaok of heater perform- anaa) 11. Tharmomatar wall 0 360* C- mtraury bulb tharmomatar (vieual elieek of ooolar perform ance) 12. Solenoid valva General Control K-10-2. Control* Aroelor temperature to mewl demand* o< ayatem For automatic temperature control a oolcnoid valve, item 12, is imJtcated In a by-paasArrangement with a manuallyoperated needle valvo. The needle valve is adjusted to give almost enough Iwat to meet the requirements and the aetuai control ia carried on by tho solenoid valve, which open* and cloaca ns directed by a tornpcraturc-controi instrument connected to the equipment being One unit was act up with tomperatura control using a I-ecd* A Northrop Mode) 8 ell-Wcctric oootroi with droop corrector. Very clone control over a wide range of heat demand resulted, when a throttling range adjustment of 4 was uaed on thie eontrol device. Safety Circuit. Figure 3 shows a safety circuit which auto matically protects the system by dosing off tbe gas supply in the event of faulty operating conditions. Provision ia made for shutting off the warning horn while the system la being put bask into operation after a safety shutdown. A detailed Hat of the safety and oootroi equipment is given in Table VII. The equipment named indicates the type required. ACENOWLEDCMHVT9 The author* are grateful to A. M. EDenburg of Monsanto's Re search Laboratory at Anniston, Ala., for fumWilog many of the technical data about Aroelor 1348 and for assistance In preparing the msnusoript. LrruATtmg citbo (1) Allen Bradley Co., Milwaukaa. Wii., Btdi. 700. (3) Ibid., Bull. 900. (3) Am. Boe. Tasting Material*. Proe. Am. Sot. Tatting Material*. 34,53(1934). . (4) Am. Boe, Tasting Materials, "Standards oa Patrolsum prod ucts and Lubricants," 1945. (5) Drinker, C. K., J. Ind. Hyg. Tested.. 31, 155 (1939). (0) Mousauto Cliotnioel Co., Anniston, Ala., private eommunies- tion, April 13, 1944. (7) Monsanto Chemical Co.. 8t. Louis. Mo., Monsanto fee*. Bail P-115 (August 1947). (8) Sortman, C., Beatty, H., and Heron. 8., Ixo. Eno. Casts., 33, 367(1941). (9) Sullivan. M. V., Wolfs, I. K.. and Usman, W. A , Ibid., 39, 1507 (1947). (10) Underwriters' Laboratories. Chiosgo, Dl.. Mlecollanaoug Haaards," No. 2498.1984. Racgivgo August 27. 1949. Praaantod befora the MaaUag-ta-Mlrietur*. Alabama Section, Anaaicaa Caawieu. 9owrr. Daaambrr S. tS46. Fiimtsb in U. 8. A. MQNS 078^34 'V Monsanto Chemicals-Plastics MONSANTO CHEMICAL COMPANY ST. LOUIS AKRON BIRMINGHAM BOSTON CHARLOTTE CHICAGO CINCINNATI CLEVELAND o DETROIT HOUSTON LOS ANGELES NEW YORK PHILADELPHIA SAN FRANCISCO SEATTLE MONSANTO (CANADA) LTD. Montreal o Toronto o Vancovvor MONSANTO (AUSTRALIA) PTY LTD. Moibourna MONSANTO CHEMICALS LTD. London Ropraoontatlvos in tho Principal Citioo ol tho World FaOlHAO-ICDW-t-'* Print*. In U.i.A. MENS 078235